[tahoe-dev] simpler/quicker hash function combiners for more specific purposes

[Zooko O'Whielacronx]

Hm. You know, just as we don't need the full strength Comb4P if we
were using a hash for encryption (since we would need only the PRF
property and not the others) we also don't need the full strength of
Comb4P when using a hash for checking the integrity of ciphertexts,
because we need only the collision-resistance property and not the
others. The concatenation combiner is a robust combiner for collision
resistance:

H|(x) = H₀(x) | H₁(x)

Regards,

Zooko